﻿374 
  JOURNAL 
  OF 
  THE 
  WASHINGTON 
  ACADEMY 
  OF 
  SCIENCES 
  VOL. 
  12, 
  NO. 
  16 
  

  

  eggs 
  are 
  produced. 
  The 
  maximum 
  number 
  obtained 
  from 
  one 
  

   Mononchus 
  was 
  forty-one, 
  the 
  minimum 
  number, 
  twenty 
  eggs. 
  

  

  The 
  eggs 
  required 
  from 
  six 
  to 
  seven 
  days 
  before 
  hatching. 
  This 
  also 
  

   is 
  rather 
  a 
  long 
  period 
  compared 
  with 
  Rhabditis, 
  Diplogaster 
  and 
  some 
  

   other 
  known 
  forms. 
  The 
  mononch 
  eggs 
  are 
  unicellular 
  when 
  de- 
  

   posited 
  ; 
  the 
  first 
  division 
  takes 
  place 
  about 
  twenty-four 
  hours 
  later. 
  

  

  C. 
  The 
  development, 
  of 
  the 
  larva 
  of 
  Mononchus 
  papillatus. 
  — 
  The 
  

   newly 
  hatched 
  larva 
  is 
  very 
  active 
  but 
  not 
  hardy, 
  and 
  the 
  presence 
  of 
  

   soil 
  seems 
  very 
  essential 
  to 
  its 
  life. 
  The 
  body 
  is 
  quite 
  transparent. 
  

   As 
  far 
  as 
  our 
  experiments 
  show, 
  during 
  the 
  first 
  two 
  or 
  three 
  days 
  

   the 
  larvae 
  attacked 
  no 
  nemas 
  ; 
  but 
  on 
  the 
  fourth 
  day, 
  and 
  even 
  on 
  the 
  

   third 
  day, 
  the 
  predatory 
  instinct 
  was 
  developed 
  and 
  they 
  began 
  to 
  

   feed 
  on 
  other 
  nemas. 
  As 
  soon 
  as 
  this 
  occurred 
  the 
  intestine 
  began 
  

   to 
  darken 
  and 
  in 
  a 
  short 
  time 
  became 
  opaque. 
  

  

  The 
  time 
  of 
  larval 
  development 
  up 
  to 
  the 
  period 
  of 
  sexual 
  maturity 
  

   was 
  somewhat 
  varied. 
  Slide 
  cultures 
  showed 
  the 
  average 
  time 
  for 
  

   larval 
  development 
  (from 
  the 
  end 
  of 
  embryonic 
  life 
  in 
  the 
  egg 
  shell 
  to 
  

   sexual 
  maturity) 
  to 
  be 
  from 
  six 
  to 
  seven 
  weeks. 
  But 
  tube 
  cultures 
  

   showed 
  the 
  minimum 
  time 
  to 
  be 
  only 
  four 
  and 
  one-half 
  weeks. 
  The 
  

   temperature 
  of 
  these 
  cultures 
  was 
  the 
  same, 
  and 
  the 
  difference 
  in 
  re- 
  

   sults 
  must 
  be 
  due 
  to 
  the 
  more 
  natural 
  environment 
  found 
  in 
  the 
  tubes. 
  

   Therefore 
  we 
  are 
  inclined 
  to 
  adopt 
  the 
  minimum 
  time 
  as 
  the 
  time 
  re- 
  

   quired 
  for 
  development, 
  and 
  to 
  judge 
  from 
  this 
  the 
  influence 
  of 
  this 
  

   species 
  upon 
  the 
  nematode 
  population 
  of 
  the 
  soil. 
  

  

  Unfortunately, 
  up 
  to 
  the 
  present, 
  we 
  have 
  not 
  been 
  able 
  to 
  get 
  exact 
  

   data 
  as 
  to 
  the 
  time 
  and 
  number 
  of 
  the 
  moultings. 
  We 
  observed 
  three 
  

   moults, 
  two 
  in 
  the 
  earlier 
  stages 
  of 
  growth 
  and 
  one 
  just 
  before 
  arrival 
  

   at 
  sexual 
  maturity. 
  In 
  a 
  study 
  of 
  the 
  life 
  history 
  of 
  one 
  specimen 
  we 
  

   observed 
  a 
  moult 
  at 
  eighteen 
  days 
  and 
  another 
  at 
  forty-four 
  days 
  after 
  

   hatching, 
  the 
  latter 
  being 
  the 
  moult 
  just 
  before 
  sexual 
  maturity. 
  

   Judging 
  from 
  the 
  size 
  of 
  the 
  nema 
  at 
  which 
  other 
  moultings 
  were 
  

   observed, 
  there 
  must 
  be 
  a 
  moult 
  between 
  eighteen 
  and 
  forty-four 
  days. 
  

   There 
  may 
  be 
  a 
  moult 
  soon 
  after 
  hatching, 
  but 
  we 
  never 
  observed 
  it. 
  

   The 
  skin 
  is 
  shed 
  as 
  a 
  whole. 
  There 
  were 
  no 
  observations 
  of 
  the 
  act 
  

   of 
  moulting, 
  but, 
  judging 
  from 
  the 
  cast, 
  the 
  animal 
  leaves 
  the 
  skin 
  

   through 
  an 
  opening 
  in 
  the 
  ventral 
  side 
  near 
  the 
  cardia. 
  The 
  mouth- 
  

   capsule 
  and 
  wall 
  of 
  the 
  rectum 
  were 
  found 
  attached 
  to 
  the 
  cast; 
  the 
  

   lining 
  of 
  the 
  oesophagus 
  was 
  not 
  observed 
  and 
  may 
  be 
  cast 
  off 
  sepa- 
  

   rately. 
  The 
  animal 
  became 
  rather 
  sluggish 
  and 
  inactive 
  just 
  before 
  

   each 
  moult. 
  

  

  